By Dr. Tim Trader ND, PhD
There are several claims and possible misconstrued ideas that fruit may not be as healthful as we have been led to believe. There have been allegations that fruit may increase blood glucose and escalate diabetes risk or if anything fruit may not be a good food for diabetics. Fruit has been accused of being an underlying factor in insulin resistance, a known causative factor in diabetes. It has been said that fruit may increase inflammation and intern boost heart disease, especially in diabetics. It is thought that fruit may also increase Advanced Glycation End Products (AGEs) and this, in turn, would also accelerate heart disease along with other chronic diseases like autoimmune disease.
There is more concern about fruit, as there has been apprehensiveness that fruit may contribute to cancer creation and growth. Fruit may even disrupt apoptosis, or programed cells death, an internal program that cells rely on to keep from turning into cancer cells. Fruit has also been condemned as a causation of tooth decay and cavities. And fruit consumption may lead to a shorter life, in part due to the diabetes correlation, inflammation, and heart disease, at least that is the theory. There is no wonder why people are concerned about fruit consumption, including physicians and nutritionists.
Let us look at where some of these ideas come from and just what the science is about consuming fruits. Are these concerns justified or are they mere speculation built on assumptions? These assumptions that may just disappear when they are looked at in scientific light and serious depth.
Fruit & diabetes
Let us start with the notion that fruits raise blood sugar and can cause diabetes. It seems that most of this line of thinking comes from the science of refined sugars, like sucrose (table sugar) and high fructose corn syrup. And yes, there is a tie to eating sucrose and type 2 diabetes, whether it is spooned on your food or already in highly processed foods you eat. 1 Though just adding sugar is not the major cause of type 2 diabetes, it is a contributor, the real instigator of type 2 diabetes is insulin resistance. Processed foods increase your blood glucose levels and if your cells can’t take in the glucose, what is called insulin resistance, then the glucose stays floating around in your blood stream causing havoc. High Fructose corn syrup, likewise, has been tied to type 2 diabetes, which we see higher rates of diabetes in societies that have an above average high fructose corn syrup consumption. 2 Since fruit is known to have sugar and carbohydrates as their main calories, tying fruit to table sugar and additives like high fructose corn syrup, seems to be a logical step.
So, what does the science about fruits say…
Because of the make-up of fruit, which not only is an array of sugars but also fiber, nutrients, phytochemicals, and slower digesting carbohydrates, fruit does the opposite of what added sugar does to promote type 2 diabetes. 3 It is about consuming the whole food without adding more sugar on top of it, that allows the body to take in the sugar and utilize it properly. Slower absorption of sugar and nutrients to help that body make use of the sugar properly makes a whole difference in sugar utilization. Even eating more than the average fruit intake has been shown to lower type 2 diabetes risk. 4 High fruit consumption not only lowers the diabetes risk but has also been shown to lower risks of developing major vascular complications. 5 Since a lot of fruits have naturally occurring fructose, we find that fruit also does not have the same reaction as high fructose corn syrup in the case of diabetes. 6 But, fruit actually allows the body to use the fructose properly and not raise fasting blood sugars or hemoglobin A1C (which are the preliminary tests that determine diabetes.)
Fruit, Heart Disease and Inflammation
Not only has fruit been shown to prevent and reduce diabetes, but fruit has also been shown to reduce cardiovascular disease. 7 which brings up another issue, the issue of inflammation and with inflammation you need to talk about advanced glycation end products (AGEs). Taking in sugar has shown to create advanced glycation end products (AGEs) 8 High fructose corn syrup actually causes inflammation and increases advanced glycation end products (AGEs) as well. 9 Not only does advanced glycation end products raise inflammation there is a strong tie with asthma, chronic bronchitis and arthritis along with cardiovascular disease. But fruit has the opposite effect 10 because to start with, fruits are low in (carboxylmethyl)-L-lysine (an advanced glycation end product.) 10, 11 In reality, fruit actually lowers inflammation as well as oxidative stress, which also contributes to inflammation. 12
Another cause of inflammation is insulin resistance. Insulin resistance is where cells of your body do not respond to insulin. Insulin resistance keeps the glucose in your blood stream from entering your cells, where it is needed. This in turn, keeps glucose floating around in your blood stream causing inflammation and your cells are starving for the food they need. The bodily cells cry out for glucose by signaling the pancreas to produce more insulin in an attempt to overwhelm the blockages that are keeping the glucose from getting into the cells. 13 The long-term presence of a high glucose in the blood (hyperglycemia) is irritating to the walls of the blood vessels and they react to produce inflammation, but it is not just to the blood vessel walls that become inflamed, but all across the body and eventually this inflammation can lead to organ damage. 14,15,16 Insulin resistance is not caused by high sugars but by high amounts of fat in the cells. This high amount of fat blocks the insulin receptors so that insulin does not open the cell receptor to take in glucose. 17, 18 As for fruit, even increasing your fruit intake has been shown to not increase insulin resistance. 19 This is because it is not the sugars that are causing the insulin resistance but a high fat diet.
This is where sugars affect the cardiovascular system, the more inflammation, the harder it is on the heart and the whole of the cardiovascular system. Get rid of the inflammation and you ease the burden of the whole system, the whole body.
Fruit and Cancer
There is evidence that cancer cells grow best in a high glucose environment. Cancer cells need the sugar to fuel their rapid, uninhibited growth. 20 Cancer growth is most prevalent when a person is insulin resistant and has hyperglycemia. 21,22 With an abnormally high glucose state where sugar is overly abundant you feed the cancer and in a healthy overall glucose balance the sugar is not there to assist the cancer growth. 23,24 When glucose is overly abundant, it makes it easier for cancer cells to get the energy source it is looking for. As stated earlier, fruits have been shown to not only help curtail insulin resistance, but fruits have demonstrated to reduce the risk of cancer. 25 Fruits reduce the risk of breast cancer. 26 Fruit may reduce the risk of lung cancer by 40%, 27, 28 even a higher consumption of fruit has been established to reduce the risk of lung cancer even for smokers. 29 Higher fruit intake has been correlated with lower childhood leukemia as well. 30 There are no fruits listed as cancer causing agents, other than those which have pesticides on them. The conclusion is that fruits don’t cause cancer 31 and they most probably will help the body fight the cancer. 32
Fruit and Weight Gain
There are some warnings saying that fruit can cause weight gain. We know that high sugar and fructose consumption itself have been known to induce weight gain and has a major role in causing obesity. 33 But, is that the same for consuming fruit? Fruit is high in fiber and water; both help control sugar absorption and dietary satiation. Fiber slows down the sugar absorption, so it is better handled in the body, less rise in blood glucose. 34 let us take as an example the famous McDonald’s Big Mac and compare it to fruit. The Big Mac has 550 calories in each sandwich, it has 1.9 grams of fiber, 116 grams of water and weighs in at just over 7 ounces. 35 To get the same number of calories from oranges, it would take 9 medium oranges, weighing in at almost 42 ounces. The water content is 1139 grams and over 29 grams of fiber. 35 The oranges are 6 times the weight of the Big Mac, almost 10 times the amount of water of the Big Mac, and 15 times the fiber content of the Big Mac. Fiber and water content affect being satisfied. 36, 37 The higher volume, water content and fiber creates satiation quicker and so you eat less. With fruits you are more satisfied with less calories and as a bonus you get better nutrition.
The reality is that fruit can help keep you from gaining weight due to many factors, like the fiber slowing down the sugar intake. The higher water content of fruit along with the fiber can make you fuller, quicker, and more satisfied with less calories and less calories keeps you from gaining weight. When you eat fruit, it can actually bring the weight down. 38 Obviously you are more satiated and satisfied when eating fruit then when you eat processed foods. Not only will fruit not put the weight on you, but it may also prevent obesity 39, 40 Higher fruit content in a diet even beats out eating more vegetables in preventing obesity. 41 Eating fruit seems to be very helpful instead of making things worse.
Fruit and Dental Cavities
Once again fruit is compared to sugar in the cause of cavities. Yes, high consumption of sugar, in the form of candy and processed foods have been shown to be a major cause of dental cavities. 42 There seems to be 3 major reasons food can help create dental cavities: bacterial affinity of the food, food stickiness, and acidity. Though if the food does not remain on the teeth, then it won’t matter if the bacteria (that create the cavities) have an affinity for the food. Since fruit does contain sugars, the first item needed to be attended to is if the fruit is sticking to the teeth. The assumption is that fruit has to stick to the teeth, but in reality, fruit is one of the most rapidly clearing foods that we can eat, even bananas and apples clear off the teeth, so quickly, that scientists can’t even find enough to test. 43
Very acidic food can erode the enamel on your teeth, leaving more room for cavities to form. Of course, some very acid foods are fruits, foods like citrus can be highly acidic. Some of the least acid foods are green leafy vegetables, like romaine lettuce or spinach. To measure acidity the pH scale is used, lower numbers are more acidic and higher numbers are alkaline. The pH number of 7 represents neutral. All foods are pretty much on the acid side of the pH scale. Romaine lettuce comes in around 5.78 to 6.06 and Spinach at 5.1 to 5.7, closer to the neutral number of 7. Some examples of fruit are Bananas 4.5 to 5.2, Dates 6.2 to 6.4, Pomegranate 6.72 to 6.82, Papaya 5.5- 5.9, Watermelon 5.18-5.60, and Mango 5.8 -6.0. all of which comes in very close to the green leafy vegetable’s pH of 5 to 6. 44, 45, 46 To compare, lemon juice comes in around a pH of 2.0 and if you were to drink lemon juice, maybe a suggestion of brushing your teeth and rinsing soon after ingesting the lemon juice would be appropriate. For the most part, fruits are just as easy on your tooth enamel as leafy green vegetables.
Here is an extra benefit of fruits, there are some phytonutrients in fruit that actually prevent the adherence of bacteria to the teeth and prevent plaque formation. 47 one such phytonutrient from grapes is so effective that they have tried to isolate it make it into an additive for processed foods to prevent plaque formation on teeth. Since we are talking about plaque formation, they have also found that phytonutrients found in fruit also reduce plaque formation in your arteries. 48 Another benefit for those with cardiovascular disease.
Other Benefits of Fruit
Speaking of phytonutrients, one of the best-known benefits of fruit is the antioxidant content of fruit. The antioxidant content in fruit has been shown to reduce the risk for many diseases. 49 And fruits are loaded with antioxidants. 50 Antioxidants like polyphenols, and polyphenols are a category of phytonutrients that include such antioxidants like anthocyanidins, flavanols, and isoflavones, to mention a few, all of which has numerous antioxidant effects. 51, 52 Fruit polyphenols also are anti-inflammatory, 53 which help in many diseases like diabetes 54 and a general improvement in health. 55 The specific polyphenol, anthocyanidins has been shown to antiangiogenic affect, 56 which means it reduces the blood flow to tumors, essentially helping to starve the caner. Fruit antioxidants are a really beneficial.
Fruit is also essential to your gut health. The prebiotics fruit contains help feed the gut microbiome (the beneficial bacteria and other microbes in your intestinal tract) fruit is essential for keeping a healthy balance of gut microbiota. 57 Eating fruit keeps a balance in your intestinal tract, which alleviates bowel and skin troubles as well fruit can help with fatigue via the gut microbiome. 58 As Hippocrates said, “all disease begins in the gut” and if you have a healthy gut, you ultimately help your whole body be healthy.
Fruit and Longevity
What it all comes down to, will eating fruit enable you to possibly live longer and without disabling disease? The answer is that fruit is associated with a lower risk of all-cause mortality, particularly cardiovascular mortality. 59 This means it lowers your risk for chronic disease. And eating less fruit is associated with progressively shorter survival. 60
There is this massive study, called the Global Burden of Disease Study 61 which came to the conclusion that the 5 top leading risks of death were dietary, smoking, high blood pressure, high body mass index, and physical inactivity…in that order. Dietary risks is at the top of the list, even above smoking. They also said, “with the most prominent dietary risks being diets low in fruits.” 62 Not getting enough fruit was responsible for an estimated 4.9 million deaths a year around the world. This is all about simply eating fruit.
The World Health Organization’s International Agency for Research on Cancer has said that eating fruit can prevent cancer up to 30% worldwide. 63 This alone can increase your longevity.
Why be afraid to eat fruit when there is all of this evidence that supports fruit as being a vital part of a healthy diet. Fruit helps with diabetes, heart disease, and cancer. It keeps you from being obese and having dental issues. Fruit is full of nutrients that keep you nutrient efficient and reduce inflammation. And fruit keeps you living longer without disabling diseases. Almost sounds too good to be true, but it is true, and it is a simple solution to creating health.
1 Metabolic effects of dietary sucrose in type II diabetic subjects https://pubmed.ncbi.nlm.nih.gov/8404438/
2 High fructose corn syrup and diabetes prevalence: a global perspective https://pubmed.ncbi.nlm.nih.gov/23181629/
3 High-carbohydrate, high-fiber diets for insulin-treated men with diabetes mellitus https://pubmed.ncbi.nlm.nih.gov/495550/
4 Fruit consumption and risk of type 2 diabetes: results from three prospective longitudinal cohort studies https://pubmed.ncbi.nlm.nih.gov/23990623/
5 Fresh fruit consumption in relation to incident diabetes and diabetic vascular complications: A 7-y prospective study of 0.5 million Chinese adults https://pubmed.ncbi.nlm.nih.gov/28399126/
6 Dietary Fructose and Metabolic Syndrome and Diabetes https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2714385/
7 Pathways and mechanisms linking dietary components to cardiometabolic disease: thinking beyond calories https://onlinelibrary.wiley.com/doi/epdf/10.1111/obr.12699
8 Toxic AGEs (TAGE) theory: a new concept for preventing the development of diseases related to lifestyle https://dmsjournal.biomedcentral.com/articles/10.1186/s13098-020-00614-3
9 Formation of Fructose-Mediated Advanced Glycation End Products and Their Roles in Metabolic and Inflammatory Diseases https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5227984/
10 Dietary advanced glycation end products and their relevance for human health https://www.sciencedirect.com/science/article/pii/S1568163718301193
11 The advanced glycation end product, Nepsilon-(carboxymethyl)lysine, is a product of both lipid peroxidation and glycoxidation reactions https://pubmed.ncbi.nlm.nih.gov/8626637/
12 Fruit and vegetable consumption and its relation to markers of inflammation and oxidative stress in adolescents https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2676354/
13 Insulin Resistance & Prediabetes https://www.niddk.nih.gov/health-information/diabetes/overview/what-is-diabetes/prediabetes-insulin-resistance
14 Inflammation and insulin resistance https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1483173/
15 New insights into insulin: The anti-inflammatory effect and its clinical relevance https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3992527/#:~:text=Hyperglycemia%2C%20a%20commonly%20exhibited%20metabolic,eventually%20leads%20to%20organ%20damage.
16 Metabolic Inflammation and Insulin Resistance in Obesity https://www.ahajournals.org/doi/10.1161/CIRCRESAHA.119.315896#:~:text=Although%20insulin%20resistance%20may%20precede,conditions%20or%20stages%20of%20obesity.
17 Skeletal intramyocellular lipid metabolism and insulin resistance https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4762133/
18 Mechanism of free fatty acid-induced insulin resistance in humans. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC507380/
19 Dose-response effect of fruit and vegetables on insulin resistance in people at high risk of cardiovascular disease: a randomized controlled trial https://pubmed.ncbi.nlm.nih.gov/24130354/
20 Cancer as a metabolic disease: implications for novel therapeutics https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3941741/
21 Effect of elevated basal insulin on cancer incidence and mortality in cancer incident patients: the Israel GOH 29-year follow-up study https://pubmed.ncbi.nlm.nih.gov/22619079/
22 Insulin resistance and cancer: the role of insulin and IGFs https://erc.bioscientifica.com/view/journals/erc/20/1/R1.xml
23 High glucose levels boost the aggressiveness of highly metastatic cholangiocarcinoma cells via O-GlcNAcylation https://www.nature.com/articles/srep43842#:~:text=Introduction,bladder2%2C3%2C4.
24 Effects of hyperglycemia on the progression of tumor diseases https://jeccr.biomedcentral.com/articles/10.1186/s13046-019-1309-6
25 Breast cancer risk in relation to the joint effect of BRCA mutations and diet diversity https://pubmed.ncbi.nlm.nih.gov/19165595/
26 Fruit and vegetable consumption in adolescence and early adulthood and risk of breast cancer: population based cohort study https://www.bmj.com/content/353/bmj.i2343
27 Fruits and Vegetables Are Associated with Lower Lung Cancer Risk Only in the Placebo Arm of the β-Carotene and Retinol Efficacy Trial (CARET) https://aacrjournals.org/cebp/article/12/4/350/255235/Fruits-and-Vegetables-Are-Associated-with-Lower
28 Fruits, vegetables and lung cancer risk: a systematic review and meta-analysis https://pubmed.ncbi.nlm.nih.gov/26371287/
29 The Associations of Fruit and Vegetable Intake with Lung Cancer Risk in Participants with Different Smoking Status: A Meta-Analysis of Prospective Cohort Studies https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6723574/
30 Food consumption by children and the risk of childhood acute leukemia https://pubmed.ncbi.nlm.nih.gov/15561989/
31 Fruit and vegetables and cancer risk https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3039795/#:~:text=In%20the%20recent%20large%20prospective,smoking%20and%2For%20alcohol%20consumption.
32 Vegetables, fruit, antioxidants and cancer: a review of Italian studies https://pubmed.ncbi.nlm.nih.gov/11876489/#:~:text=Fruit%20was%20related%20to%20a,esophageal%20and%20breast%20cancer%20risk.
33 Fructose, weight gain, and the insulin resistance syndrome https://pubmed.ncbi.nlm.nih.gov/12399260/
34 Effects of dietary fiber and carbohydrate on glucose and lipoprotein metabolism in diabetic patients https://pubmed.ncbi.nlm.nih.gov/1663443/
35 NCCDB nutrition coordinating center & nutrient database (University of Minnesota)
36 The effect of fiber on satiety and food intake: a systematic review https://pubmed.ncbi.nlm.nih.gov/23885994/
37 Effect of Pre-meal Water Consumption on Energy Intake and Satiety in Non-obese Young Adults https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6209729/#:~:text=More%20test%20meal%20studies%20have,an%20effect%20on%20energy%20intake.
38 Effects of fruit consumption on body mass index and weight loss in a sample of overweight and obese dieters enrolled in a weight-loss intervention trial https://pubmed.ncbi.nlm.nih.gov/20022464/
39 Impact of Whole, Fresh Fruit Consumption on Energy Intake and Adiposity: A Systematic Review https://www.frontiersin.org/articles/10.3389/fnut.2019.00066/full
40 Frequency of consumption of whole fruit, not fruit juice, is associated with reduced prevalence of obesity in Korean adults https://www.jandonline.org/article/S2212-2672(18)31317-0/fulltext
41 Higher Intake of Fruit, but Not Vegetables or Fiber, at Baseline Is Associated with Lower Risk of Becoming Overweight or Obese in Middle-Aged and Older Women of Normal BMI at Baselinehttps://academic.oup.com/jn/article/145/5/960/4616100
42 Added Sugar and Oral Health: A Position Paper of the Brazilian Academy of Dentistry https://pubmed.ncbi.nlm.nih.gov/35464781/
44 US FDA pH of foods and food products
45 Lack of correlation between food retention on the human dentition and consumer perception of food stickiness https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/papayas#:~:text=Papaya%20is%20a%20low%2Dacid,tartness%20of%20the%20papaya%20fruit.
46 Clemson pH values of common foods and ingredients
47 Inhibitory effects of the phenolic fraction from the pomace of Vitis coignetiae on biofilm formation by Streptococcus mutans https://pubmed.ncbi.nlm.nih.gov/22284343/
48 The Impact of Dietary Supplementation of Whole Foods and Polyphenols on Atherosclerosis https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7400924/
49 Effect of fruit and vegetable antioxidants on total antioxidant capacity of blood plasma https://pubmed.ncbi.nlm.nih.gov/24698344/
50 Relationship between color and antioxidant capacity of fruits and vegetables https://www.sciencedirect.com/science/article/pii/S2665927119300097
51 Identification of the 100 richest dietary sources of polyphenols: an application of the Phenol-Explorer database https://www.nature.com/articles/ejcn2010221
52 Simultaneous Determination of All Polyphenols in Vegetables, Fruits, and Teas https://pubs.acs.org/doi/10.1021/jf020926l
53 Fruit Polyphenols: A Review of Anti-inflammatory Effects in Humans https://pubmed.ncbi.nlm.nih.gov/25616409/
54 Natural and Artificial Flavoring Agents and Food Dyes Handbook of Food Bioengineering Chapter 7 - Fruits: A Source of Polyphenols and Health Benefits https://www.sciencedirect.com/science/article/pii/B9780128115183000077
55 Contents of polyphenols in fruit and vegetables https://www.sciencedirect.com/science/article/abs/pii/S0308814604008222
56 Anthocyanidins and anthocyanins: colored pigments as food, pharmaceutical ingredients, and the potential health benefits https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5613902/
57 Dietary fruit and vegetable intake, gut microbiota, and type 2 diabetes: results from two large human cohort studies https://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-020-01842-0#:~:text=Fecal%20metabolome%20analysis%20revealed%20specific,improving%20intestinal%20ecology%20%5B17%5D.
58 An exploratory study on the effect of daily fruits and vegetable juice on human gut microbiota https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6170287/
59 Fruit and vegetable consumption and all-cause mortality: a dose-response analysis https://pubmed.ncbi.nlm.nih.gov/23803880/
60 Fruit and vegetable consumption and mortality from all causes, cardiovascular disease, and cancer: systematic review and dose-response meta-analysis of prospective cohort studies https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4115152/
61 The state of US health, 1990-2010: burden of diseases, injuries, and risk factors https://pubmed.ncbi.nlm.nih.gov/23842577/
62 A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions, 1990-2010: a systematic analysis for the Global Burden of Disease Study 2010 https://pubmed.ncbi.nlm.nih.gov/23245609/
63 The global burden of disease attributable to low consumption of fruit and vegetables: implications for the global strategy on diet https://scielosp.org/article/bwho/2005.v83n2/100-108/en/